Another clutch basket failure.

The studs are 9 mm diameter, so very difficult (impossible?) to find flat head screws in that size. I've settled on drilling the clutch basket and spring plate out to take 3/8-24 fasteners, countersunk the basket for them, and bored the spacers out to fit. I've put it together and checked for clearance behind the ring gear. Plenty of room there. I'm now in the process of drilling the ring gear for dowel pins. That's some hard steel! I've drilled holes for the two pins in a smaller diameter, because I don't have a carbide drill and reamer the right size. Should have them in a few days, so I expect to have the bike back on the road soon.

These are the new fasteners. The bolts are high strength military surplus stuff that I've had for years. Fortunately, I had exactly 4 of them in the right size. The jet nuts are also surplus items from way back.



I'll post some pictures of the assembled unit when I'm done.

Ken

TonyA said:

David Coote's 2013 basket is billet . My late 2014 is cast . So 2014 , yours looks cast like mine and part of that MK2 process . I think a lot of the clutch issues boil down to quality of assembly . At 6,500 miles my clutch basket was good and tight . I have not looked in 9,000 miles. I have a new Norton clutch basket on order , I am still waiting to hear back from Norton . If I can get a new one , I will post the condition of my current one.

Click to expand...

Mine is a December 2014 build, so I think you are right that the change occurred earlier in 2014.

Ken

Seems like you’re on the right track to a fix. Definitely dowel the ring gear while its out. Take no chances!!! Heres an interesting fact: There is NO date that parts improve or get worse. In fact, we’ve now rebuilt 8 engines. And of course I get emails and pics daily from others. In italy 2 bikes just sheared ring gears. My dads 2013 came in the same crate as a local Norton owner named vic from Toronto. He just completed my dads school (if you want to call it that). Where vic tore down the engine, replaced all shitty components with quality bits, balanced and blue printed the engine. We went for a nice ride. Pics on my IG @112norton. The internals were very different. Things we thought were updated 2 yrs later. Were already in his bike. We have a 2016 Domi SS with older parts from 2013 from factory. There is NO year better than another. MKII means nothing!!! All bullshit marketing. Cosmetic changes. So I advise everyone to open up your engine cases and take a look. Due to covid I never got to video a rebuild but promise I will. Plus share all of our upgrades. Check everything. The things we’ve seen are mind blowing. Its like the factory didn’t expect anyone to ride them. They are super unsafe machines until you can prove otherwise. If you have high mileage you are lucky. Dialled in they are amazing. 80% of issues are assembly issues and incoming quality control or lack of. The other 20% is cheap fake components like all the fake knock off electrical sensors and cheap bearings. There is hardly any fit and finish in the engine. Sure hand built is great. But only if you train and audit your employees. Some bikes are incredible. Its mind blowing how others didn’t get trained to the same level.


Ken, if you have any questions, PM me.

richard-7 said:

Seems like you’re on the right track to a fix. Definitely dowel the ring gear while its out. Take no chances!!! Heres an interesting fact: There is NO date that parts improve or get worse. In fact, we’ve now rebuilt 8 engines. And of course I get emails and pics daily from others. In italy 2 bikes just sheared ring gears. My dads 2013 came in the same crate as a local Norton owner named vic from Toronto. He just completed my dads school (if you want to call it that). Where vic tore down the engine, replaced all shitty components with quality bits, balanced and blue printed the engine. We went for a nice ride. Pics on my IG @112norton. The internals were very different. Things we thought were updated 2 yrs later. Were already in his bike. We have a 2016 Domi SS with older parts from 2013 from factory. There is NO year better than another. MKII means nothing!!! All bullshit marketing. Cosmetic changes. So I advise everyone to open up your engine cases and take a look. Due to covid I never got to video a rebuild but promise I will. Plus share all of our upgrades. Check everything. The things we’ve seen are mind blowing. Its like the factory didn’t expect anyone to ride them. They are super unsafe machines until you can prove otherwise. If you have high mileage you are lucky. Dialled in they are amazing. 80% of issues are assembly issues and incoming quality control or lack of. The other 20% is cheap fake components like all the fake knock off electrical sensors and cheap bearings. There is hardly any fit and finish in the engine. Sure hand built is great. But only if you train and audit your employees. Some bikes are incredible. Its mind blowing how others didn’t get trained to the same level.


Ken, if you have any questions, PM me.

Click to expand...

Thanks for responding Richard. I do intend to pin the ring gear. It is hard enough that it requires carbide tools to drill. I've laid out the holes for two 1/4" dowels and started by center drilling them with a carbide center drill. A proper size carbide drill and carbide reamer should arrive tomorrow so I can finish it, then back together. I'm tempted to tear it down further while I have it on the lift, but this is riding season, and I haven't had any engine problems or noises, so I think I'll put that off until the end of the year. It only had ~400 miles on it when I bought it, and it quit putting much oil in the air box after a few hundred more miles. I'm sneaking up on 6,000 miles now, and I drain it after every ride, but it's usually just a few drops. So I don't feel like I'm at immediate risk there. I do like the idea of checking the center bearing retainer bolts and maybe balancing the crankshaft and balance shaft, but that can wait for a while.

Please continue to share the updates you and your dad are doing. I plan to keep this bike until I can't ride any more, so I'm happy to do anything that makes it better, faster, more comfortable, etc. Besides, this kind of stuff is my hobby after all.

Ken

So when you move off the springs compress and what happens first - the springs compress to their maximum or the rivet spacer hits the end of the slot?

Klaus just pointed out an error in one of the assembly pictures on the first page, and I've edited it to provide a note to that effect.

Ken

Clive said:

So when you move off the springs compress and what happens first - the springs compress to their maximum or the rivet spacer hits the end of the slot?

Click to expand...

I don't think the spacer ever hits the end of the slot, but to be sure, I'll have to check that when I assemble the clutch.

Ken

Would be interesting to see if a ball/ramp style plate could be modified to fit... voila! slipper clutch commando

Here is my hypothesis of why the rivets fail.

The collars do not provide even lateral support, as would a boss integral with the basket do. Because of clearance, the collar will tip, applying a point load on the rivet. Thus the rivet will also tip, and the bucked tail will be loaded on a fraction of its perimeter. This it will not endure for long, and the bucked tail will be pryed off at one side and subsequently on the other side as the ring gear slams back and forth.

Sketch:



An improvement would be to provide a clutch basket with integral bosses instead of the collars. Maybe bosses can be welded to the existing clutch basket?

See these videos for a dissection of similar clutches with torsion springs and comments about their design faults.

BMW K1200:
Suzuki DL1000:




-Knut

mdt-son said:

Here is my hypothesis of why the rivets fail.

The collars do not provide even lateral support, as would a boss integral with the basket do. Because of clearance, the collar will tip, applying a point load on the rivet. Thus the rivet will also tip, and the bucked tail will be loaded on a fraction of its perimeter. This it will not endure for long, and the bucked tail will be pryed off at one side and subsequently on the other side as the ring gear slams back and forth.

-Knut

Click to expand...

Agree with you totally there - maybe if the rivets had much larger heads and, instead of peening the end over, a collar was tig/mig welded onto the other end of the rivet. Any experienced welders think this is possible? Just can't convince myself that nuts/bolts would not move. Maybe wired on?

Drop in some good quality springs and dowel the ring gear and we might have a serviceable unit. When it was new my 2018 CR clutch felt fine so to get back to that and stay like it would be ok for me.

The design objective is to bring a sufficient clamping force onto the spring keeper. This is possible either by using proper rivets supported from underneath by a sturdy casting boss _AND_ a steel washer bonded to it (maximize friction and minimize pressure!), OR a reverse bolt, similarly supported and having a long threaded section which screws into the clutch basket and boss using a Time-Sert insert. The bolt needs to be locked once it has been pre-stressed. Both solutions require a new clutch basket (for trial runs, a clutch basket made of billet material will do).

On second thought, I don't believe a spacer/collar welded to the existing basket is worth it. Obtaining the necessary position tolerance will be very demanding. Full pen welding has to be done by laser so as not destroy heat treatment of the basket and spacer. Given the time factor, my bet is on a new die-cast basket. If someone from TVS is reading this, maybe they will step in?

-Knut

mdt-son said:

If someone from TVS is reading this, maybe they will step in?

-Knut

Click to expand...

I spoke to someone at Norton very recently who said that they weren't aware of an inherent problem with the clutches. I suggested that this could be because the majority of bikes have very low mileage on them but a handful of us who use our bikes properly are seeing failures often just after warranty and it would be worth someone from the new regime to monitor the forum to learn from the experiences of us unpaid product testers. Although they may be immune from 'old' warranty and 'merchantable quality' claims at the moment it could help them improve the product and avoid future claims which they would be liable for.

Yes ! I agree totally. The clutch needs a better design . Could the nuts be agent locked with castle nut lock pin through hole in bolt ? Either way I think what Ken is doing could be much better than what Norton had in there . The countersunk screw heads/precisely drilled holes should help with the anti-tilt . I don't want to use that clutch for drag racing ! Why they couldn't get a properly designed clutch from the start is SO disappointing !

Clive said:

I spoke to someone at Norton very recently who said that they weren't aware of an inherent problem with the clutches. I suggested that this could be because the majority of bikes have very low mileage on them but a handful of us who use our bikes properly are seeing failures often just after warranty and it would be worth someone from the new regime to monitor the forum to learn from the experiences of us unpaid product testers. Although they may be immune from 'old' warranty and 'merchantable quality' claims at the moment it could help them improve the product and avoid future claims which they would be liable for.

Click to expand...

WOW , That is near unbelievable ! Not aware of any issues with their clutch . That is the weakest link in their powertrain !

I have been asked to bring my attention to this post.
This design assembly with the rivets is quite normal and can be found on almost any motorcycle engine (all be it there should be six rivets).
The small collars provide a controlled clearance to allow the basket to move under the control of the cush drive springs.
The basket and gear assembly have a thin shim washer and Belleville washer to provide lateral pressure.

The rivets are (or should be) machined to 08.8mm diameter to a H7/h7 fit to the collars.
They are of a mild steel type (as with most clutch rivets) and are subject to a controlled Annealing process. This is very important, because upon assembly the rivet heads are formed or 'Peened'. This not only swells the head of the rivet but also swells the shank of the rivet causing it to grip the basket,collar and retaining plate as a sandwich. The head of the rivet after peening should appear domed.
If the rivets are not Annealed correctly, then they will NOT provide the suitable grip, and will simply fall apart.

I have assembled hundreds of different clutches to this design.
When peening with a suitable Dolly, you can 'feel' if there is something wrong with the rivet.
In fact, I have had to change Heat Treatment companies because of erroneous annealing!

Please DO NOT WELD the rivet to the rear retaining plate. The plate is made from a pre heat treated steel and would not provide any safe welded purchase or penetration! You have been warned.

The billet clutches were assembled in England pre 2014. The later units with the pressure die cast baskets were assembled some where else ???
I cannot comment about their quality.

I can tell from the images that the rivets have NOT swelled, because the collars have come out easily from the assembly. Normally you would have to accurately drill out each rivet with a 08.5mm drill to the depth just bellow the rivet head (basket side) , then drift out the rivet with a 08mm diameter pin punch. You should notice only gentle hammer blows to drive the rivet out as the rivet walls collapse inwards. This indicates that it has been assembled correctly and it it doing its job as intended.

The 961 clutch design was sound up to 2014. After that I cannot comment.
However, as stated previously, it should have three pairs of two rivets (Six in total) but doesn't. There is a reason for this
Also, the gearbox design has an inherent design flow. Unfortunately at the designing stage way back before 2008, there was an oversight regarding oil flow to the centre of the clutch. Its not present. Normally oil is fed down the centre of the input shaft to feed the end support bearings and the clutch, either by splash or by pressure of pump. And / or it can be collected by the primary gear, flung outwards and caught by simple weirs in the casting and guided down towards the clutch centre. Non present Hence the nasty black appearance in the middle to the clutch assembly.

lcrken said:

OK, finally got the tools and got it apart. It appears that the rivets just came apart. I call them rivets, but it's kind of a weird design.

This is a picture of the basic parts. You can see two of the rivets to the right, along with the collars that appear to have been installed and then the rivets peened over in the plate to the right to keep them in place. But there's no sign in that plate of any marks from the pins being peened over, so I'm a little unsure of what happened here. I left the other two rivets the alloy clutch basket at the top to show where they fit. The rivets don't seem to have been any sort of interference fit in any of the pieces, so I'm just assuming from the looks of them that they were peened over poorly at the start. Or else that's just a really bad design.

View attachment 16866

And this is a picture of the same bits from the other side.

View attachment 16867

and this is a picture of the bits partially assembled to show how they fit together. There's also one of the rivets showing how the collar fits over it. The springs will fit in the obvious cutouts for them and the spring plate will go over them, and then the rivets get peened. At least that's how I think it went.

Edit - As Klaus pointed out to me, the gear is sitting on the clutch basket wrong side up. But I'm leaving it here because it still shows the arrangement of the bits.

View attachment 16868

I'm not sure where I'm going from here. My thought is that I could just assemble it and tig weld the ends of the pins to the spring plate. I think that would work OK, but would be a little sticky if I ever need to disassemble it to replace the springs.

I've heard that there were updates in the clutch design, so maybe the later ones were improved. If so, I could try to buy a new one through Norton's new parts system. But I'm not interested in that unless it is an improved design. Does anyone here know the story on the clutch changes?

Any other ideas?

The ring gear is nice and solid, but I still plan to put a couple of dowel pins in it.

It doesn't look like there is any other damage in the primary case. This is a photo of it with the parts removed.

View attachment 16869

Ken

Click to expand...

Ken,
I can't see in the images of the shim washer & Belleville washer?
Where they not present?

Nik

Nikoli said:

Ken,
I can't see in the images of the shim washer & Belleville washer?
Where they not present?

Nik

Click to expand...

Thanks for replying, Nicolai. I appreciate your expertise in this field. I did not weld the pins, but replaced them with the bolts shown above. There is a shim washer and a Belleville washer between the clutch basket and the gear. You can see the shim washer sitting in the recess in the back of the clutch basket, but I did not include the Belleville washer in the pictures. I did inlcude both in the reassembly today. I'm hoping to test it this weekend.

Ken

Success. It's back together and the really nasty sounds are gone. Still a bit agricultural sounding, but nothing to draw stares at stop lights. Looking forward to a ride this weekend. My only regret is that I forgot to replace the balancer split gear spring. I got a couple of them a while back from Richard, but just forgot all about.

These are pictures of the clutch assembly in it's final form. I did manage to finish fitting two 1/4" dowel pins in the starter gear. I must have sharpened the carbide drills a dozen times before it was done.





Ken

Hey guys,

Delighted that you small band of enlightened engineers are slowly resolving these two clutch related issues, doweling of the Ring Gear and resolving the rivets. Unfortunately I, and I suspect many others, are not really confident (read competent) with this level of open engine surgery. As usual then it feels like I can only benefit rather than contribute. Sorry for that - Richard, I’ll contribute for the manuals shortly (PayPal issues).

Rather than riding around on a time bomb, as this is starting to feel like, I am electing to follow a ‘watch and see’ approach. This will include pulling the Primary Cover (looks easy to achieve, thanks to Richard‘s manual) on each service and checking security and condition. The key to this approach of course is knowing what to check and how best to check it, without stripping beyond Primary Cover removal.

My annual mileage is relatively low as I have other machines however, the Norton is a keeper; it will be the last bike that I own when I can’t ride any more. Do we view the ‘watch and see‘ annual inspection as a legitimate approach for the mechanically challenged? If so, how best do we none mechanics check for the presence of these clutch security problems with the Primary Cover only removed?

Cap in hand as usual!

Steve
Sunshine Coast

lcrken said:

Success. It's back together and the really nasty sounds are gone. Still a bit agricultural sounding, but nothing to draw stares at stop lights. Looking forward to a ride this weekend. My only regret is that I forgot to replace the balancer split gear spring. I got a couple of them a while back from Richard, but just forgot all about.

These are pictures of the clutch assembly in it's final form. I did manage to finish fitting two 1/4" dowel pins in the starter gear. I must have sharpened the carbide drills a dozen times before it was done.

View attachment 16947

View attachment 16948

Ken

Click to expand...

Hello Ken , nice job once again. How much do you torque the 4 bolts ? This looks like a pretty good route to take for the rest of us ? I hope it last a long time.